The present invention generally relates to acoustical panels and in particular it relates to stain resistant acoustical tiles.
Acoustical panels are often prone to stains caused by water soaking into the panel. This is especially true for ceiling panels stained by water dripping from a leaky roof. Such water damage leaves a permanent visible mark on the front face of the acoustical panel which destroys the aesthetics of the overall ceiling panel grid. Water stains occur most often when starch or starch mixtures are used as internal binders within the panel. Staining is believed to be the result of scorched starch, iron compounds and dyes from recycled cellulosic fibers from newspapers (“newsprint”) being brought to the front face of the panel by water being absorbed by the panel.
Acoustical panels typically comprise binders and fibers. Starch is the most common binder used in the formation of acoustical panels. The fibers added include mineral fiber (mineral wool), glass fiber, texpanel fiber and natural fibers such as cellulose from newsprint. Fibers contribute to the wet strength of the board as it is converted from the aqueous slurry to the substantially solid cake (wet formation) before forming the finished panel. Newsprint contributes significantly to the staining of the panel. Acoustical panels may also include clays, expanded perlite, dolomite, calcium carbonate, calcium sulfate hemihydrate, flocculants and surface active agents.
Additional binders include latexes which have been added to improve panel sag resistance under high humidity since starch is hydrophilic and its binding properties degrade in the presence of high humidity. Typically, latex is added as part of the binder mix comprising both starch and latex. The latex component commonly comprises the majority of the binder mix. Latexes are hydrophobic and are not susceptible to moisture.
Current efforts to prevent water damage to acoustical panels are directed at preventing the water from entering the inner structure of the panel. One of the most common methods is the incorporation of latexes as a binder into the panel such that water is blocked from entering the inner structure of the panel. Additionally, an impermeable backing may be applied to the back side of the panel to prevent water from being absorbed into the panel. Unfortunately, such methods only redirect the water to the outer edges of the panel which can cause a “picture frame effect” to form on the facing of the panel. The “picture frame effect” results in a visible water stain framing the outer edges of the front face. This effect can be caused by water being absorbed at the edges of the panel and by the rusting of the support grid of the ceiling system.